Tag Assistant is Google’s free tool for checking which Google tags fire on your website and what they send. It shows each GA4, Google Ads and Floodlight tag, the events they record, the values passed with them and the consent state at the time, so you can confirm tracking works before you trust the reports.
How Tag Assistant works
You open Tag Assistant in your browser, enter your website’s address and connect. Your site opens in a new tab or window with a debugging connection, and Tag Assistant records everything as you click around. At the time of writing (October 2026), the web version at tagassistant.google.com works alongside a Chrome extension that keeps the connection in the same tab; the old standalone extension of the same name was retired some time ago.
The left-hand panel lists events in the order they happened: container loaded, page view, clicks, form submissions and anything your developer pushed to the data layer. Choose an event and you see:
- which tags fired and which did not, and why;
- the values sent with each tag, such as page location or transaction ID;
- the data layer contents at that moment;
- a Consent tab showing the default and updated states for storage types such as analytics_storage and ad_storage.
When you use preview mode in Google Tag Manager, it opens Tag Assistant automatically, so most people meet it that way. GA4’s DebugView then shows the same events arriving at the analytics end.
Why it matters
Reports can look normal while tracking is quietly wrong. Tag Assistant shows you the cause directly rather than leaving you to infer it from odd numbers weeks later. For a UK site, the Consent tab is particularly useful: you can load a page, decline cookies on your banner and watch whether analytics and advertising storage stay denied. That is the practical check that your setup respects visitors’ choices under PECR.
It also saves arguments with developers and agencies. A screenshot of a tag that did not fire, with the reason Tag Assistant gives, is far easier to act on than a report that says conversions look low. When an ad platform suddenly reports fewer leads, this is usually the fastest way to tell whether the tracking broke or the campaign did.
It has limits. Tag Assistant only sees Google tags and only in the session you are testing, so it will not tell you how many real visitors were affected or whether a non-Google pixel worked. Use it to confirm the mechanism, then check GA4 and the ad platforms over the following days to confirm the numbers recovered.
Common mistakes
- Testing only the home page. Problems usually sit on the conversion path: the form, the checkout, the thank-you page.
- Stopping at “tag fired”. A tag can fire with the wrong values, such as a zero order value or a missing transaction ID. Open it and read what it sent.
- Not testing the decline path. Accept-all always works. Check what happens when someone rejects cookies.
- Missing double-firing. Two GA4 page views on one load is easy to spot here and easy to miss in reports.
How to act on it
Run a short test script after every site change: load a landing page, decline cookies, check the Consent tab; reload, accept, then complete a real enquiry or test purchase and confirm the conversion tag fired once with the right values. I set out the full routine in how to check your conversion tracking works.
If the results show tags you cannot explain, that untangling is part of my performance marketing service.